Document x1ED87Y46J6LLawRLG6p4Xqng

496 CHAPTER 19 ,1958 Guide Table 5. Heatino, Capacities, and Cfm .of Branch Ducts in Extended Plenum Perimeter Systems (Concluded) section e. side TAKEOFF TO 6-INCH round pipe for sidewall and floor diffusers Extended Plenum Pressure O.lt in. Static at'160 F Furnace Plenum Pressure 0.15 in. Static at 170 P No. OF. Elbows 0 1 2 '3 : 4 *' 5 6` Actual Length from Extended Plenum to Diffuses--Feet " Btuh Cfm Btuh Cfm Btuh . Cfm Btuh Cfm Btuh Cfm ' Btuh Cfm Btuh ' Cfm 6 10 15 20 25 30; 35 40 45 50 55 60 8600 7930 7310 6740 6230 5800 123.2 120.0 116.8 114.0 111.4 109.1 8560 7900 7290 6720 6200 5740 5340 117.4 114.5 112.1 109.2 107.0 104.8 102.8 8510 7890 7300 6740 6230. 5750 5310 4960 112.7 110.0 107.6 105.3 103.1 101.0 99.0 97.4 8540 7900 7300 6780 6270 5800 5360 4960 4610 108.2 105.8 103.6 101.5 99.6 97.8 95.9 94.0 92.5 8580 7970 7370 6820 6330 5850 5410 5000 4620 4300 104.0 101.9 99.8 97.8 96.0 94.5 92.8 -91.1 89.7 88.3 8720 8080 7490 6940 6440 5960 5490 5080 4690 4320 4020 100.2 98.3 96.7 94.8 93.0 91.4 90.0 88.7 87.2 85.0 84.7 8900 8240 7630 7060 6550 6070 5600 5190 4800 4430. 4100 3810 97.0 95.1 93.4 91.9 90.2 88.8 87.3 86.2 85.0 83.8 82.6 81.5 ` Note: Where any of the first three runs from the extended plenum exceeds 20 ft and 3 elbows, count 3 extra elbows for that run. The Equivalent Length Values used and included in calculating this table are: Diffuser and Boot - 40 ft; Each Elbow = 14 ft; Side Takeoff = 20 ft. Tapered Extended Plenum Starting Collar. SECTION F:' TOP TAKEOFF TO 6-INCH ROUND PIPE FOR SIDEWALL AND FLOOR DIFFUSERS Extended Plenum Pressure 0.18 in. Static at 160 F Furnace Plenum Pressure 0.16 in. Static at 170 F No. OF Elbows Actual Length from Extended Plenum to Diffuser--Feet . 5 , 10: '15 20 25 30 35. 40 45 50 55 60 ;\\0 1 , V;:2: ;3 4 T ` 5 ' V6 ' Btuh , * Cfm ' - Btuh ' JCfm ' Btuh: s Cfm 1 . Btuh -Cfm , Btuh Cfm. Btuh' ` Cfm Btuh Cfm 8430 7800 7210 6660 6170 5700 111.2 108.8 106.3 104.4 102.2 100.2 ; ; 8450 7840 7250 `6700 6210 5730 5300 107.2 105.0 102.8 100.7 98.9 97.0 95.1 J853Q 7900 7320 6800 6280 '5790 5350 4960 103.2 101.1 99.0 97.2 95.4 93.8 92.1 90.6 8660 8020 7430 '6900 0370 5900 5450 5030' 4650 99.7 97.8 96.0 94.2 92.4 90.8 89.4 88.0 86.7 8810 .8180 7580 701Q 6500 6000 5550 5150 4750 4400 96.0 94.4 '92.8 91.2 89.7 88.0 86.8 85.7 84.3 83.1 8390 7770 7200 6650 !616Q 5700 5280 4890 4500 4170 91.4 90.0 88.5 87.2 85.8 84.5 83.2 82.4 81.0. 80.0 7980 7380 6840 6340 5880 5430 5020 4650 4290 3970 87.5 86.2 85.0 83.8 82.5 81.4 80.2 79.4 78.3 77.3 5270 4910 98.4. 96.7 4900 4560 93.4 91.9 4590 4250 89.0 87.8 4300 3990 85.3 84.2 4070 3780 82.0 81.1 3840 3580 79.0 78.3 3660 3400 76.3 75.6 'Note: Where any-of the first three runs from the extended plenum exceeds 20 ft. and 3 elbows count 3 extra elbows for that run. .. .The Equivalent Length Values used and included in.calculating this table are: Diffuser and Boot 40 ft; Each Elbow *= 14 ft; Top Takeoff = 60 ft. , Tapered Extended Plenum Starting Collar. Warm Air1Heating Systems '497 Table 6. Required Size of Extended Plenum Cfm Handled by Plenum Plenum Dimen sions Inches Cfm Handled by Plenum Plenum Dimen sions Inches 301 to 400 401 to 500 501 to 600 601 to 700 8-x 8 10 x 8 12 x 8 14 x 8 16 x 8 701 to 800 801 to 900 901 to 1000 1001 to 1100 1101 to 1200 20x8 22 X 8 24 x8 26 X 8 28 x 8 Design of Return Duct System for Perimeter Installations With perimeter systems designed in accordance with the foregoing sim plified procedures, there, is a circulating head, of only 0.05 in. water avail able on the return side of the system. It ;is therefore necessary' that the return ducts be.adequately sized and be as'short and straight as.practica- ble. The return grilles may be centrally located, and the; ducts may be located in the attic or other unheated spaces provided they are adequately insulated. Return air may be taken from basements and crawl spaces, but should not be taken from confined spaces in which the furnace is located. ' S' " The following simplified procedure5;may be Used: 1. Lay out the return-air duct system. Measure the length and count the num ber of 90 deg turns in each return duct. 2. Total the heat loss of the area served by each return duct.: y ! ' 3. Determine the required duct free area from the length of duct, the number of 90 deg turns, and the heat loss using Table 7. Also determine the free area of the return grille from Table 7. - Other Perimeter Systems " ` 1 Each of the foregoing procedures can be used with approved' furnaces which are capable of delivering their rated cfm air volume against a total Table 7. Required Size of .Return Air Grille and. Duct. For Pressure Drop Allowance of 0.05 In. (jf Water ' ' Actual Ft. a H No. OF 90 Deg a < Turns Up to 10 Ft 11to20Ft 21 to-30 Ft 31 to 40 Ft fi1 2 3 4 .5 6' 1 2 3. 4 5 6 1 2 3 4 5 6 1 2 3 4 .6 O Btuh Duct Free Area - 16 5,000 10,000 15,000 20,000 14 17 20 23 26 28 15 19 22 25 27 28 17 20 23 25 27 '29 ifc '21 -24 27 `28 30 27 32 37 42 46 49 29 34 39 43 47 49 31 36 41 45 48 51 33 38 43 -47 49 51 37 44 50 55 60 64 40 46 52 57 61 65 43 !49 54 58 63 -67 45 51 -56 61 64 67 46 54 61 66 73 78 49 57 63 69 75 79 53 60 65 71 77 82 55 62 -68 :74 -78 83 79 , 95 ' 111 126 25,000 30,000 35,000 40,000 54 64 '72 79 '86 92 58 68 75 82 88 94 62 71 78 84 91 96 66 74 .80 87, 92 98 62 73 82 89 97 104 67 76 85 93 100 106 71 80 88 95 102 108 75 84 91 99 104 110 69 82 92 101 111 119 74 85 95 106 114 121 79 91 99 108 117 124 84 94 103 113 119 126 12177 .90 100 110 130 82 ,94 105 116 124 132 87 99 109 118 128 137 92 103 113 123 130 140 158 190 221 252 50,000 00,000 70,000 80,000 89 105 119 132 146 158 95 111 124 138 150 161 102 117 129 142 155 166 108 123 135 148 158 170 10(1 122 139 154 170 181 111 129 145 161 174 184 119 137 151 165 178 189 120 14,1 158 172 181 193 117 139 158 174 191 202 127 147 164 182 195 206 135 155 171 188 200 213 144 162 178 193 203 216 128 155 175 191 208 222 140 164 182 198 214 225 151 172 188 203 219 231 160 179 195 211 222 235 284 . 316 90,000. 100,000! 141 168 188 205 225 244 153 177 195 213 232 248 164 186 201 218 240 256 173 193 209 229 244 262 154 180 200|221 247 265 166 189 209 233 252 270 176 198 217 239 258 277 185 206 227 250 265 285 gether*to -a mu^*P^e number of return air ducts join together, add the individual duct free are&sto- 10 Qetennine the free area of duct to be used |rom that point to the return air plenum of; furnace.